[Show abstract][Hide abstract] ABSTRACT: Background & aims: TPMT activity and metabolite determination (6-thioguanine nucleotides [6-TGN] and 6-methylmercaptopurine nucleotides [6-MMPN]) remain controversial during thiopurine management. This study assessed associations between patient characteristics and TPMT activity, and their impact on metabolite levels. Patients & methods: A retrospective review of the laboratory database from a French university hospital identified 7360 patients referred for TPMT phenotype/genotype determination, and/or for 6-TGN/6-MMPN monitoring. Results: Four TPMT phenotypes were identified according to TPMT activity distribution: low, intermediate, normal/high and very high. Based on 6775 assays, 6-TGN concentrations were 1.6-fold higher in TPMT-deficient patients compared with TPMT-normal patients. Azathioprine dose and TPMT genotype were significant predictors of metabolite levels. Furthermore, 6-MMPN and 6-MMPN: 6-TGN ratios were, respectively, 1.6- and 2.2-fold higher in females than in males, despite similar TPMT, 6-TGN and azathioprine doses. An unfavorable ratio (≥20) was associated with a slightly higher TPMT activity. Conclusion: These results illustrate the usefulness of pharmacogenomics and metabolite measurement to improve the identification of noncompliance and patients at high risk for toxicity or therapeutic resistance. Original submitted 13 November 2013; Revision submitted 30 January 2014.
[Show abstract][Hide abstract] ABSTRACT: Phenome-Wide Association Studies (PheWAS) investigate whether genetic polymorphisms associated with a phenotype are also associated with other diagnoses. In this study, we have developed new methods to perform a PheWAS based on ICD-10 codes and biological test results, and to use a quantitative trait as the selection criterion. We tested our approach on thiopurine S-methyltransferase (TPMT) activity in patients treated by thiopurine drugs. We developed 2 aggregation methods for the ICD-10 codes: an ICD-10 hierarchy and a mapping to existing ICD-9-CM based PheWAS codes. Eleven biological test results were also analyzed using discretization algorithms. We applied these methods in patients having a TPMT activity assessment from the clinical data warehouse of a French academic hospital between January 2000 and July 2013. Data after initiation of thiopurine treatment were analyzed and patient groups were compared according to their TPMT activity level. A total of 442 patient records were analyzed representing 10,252 ICD-10 codes and 72,711 biological test results. The results from the ICD-9-CM based PheWAS codes and ICD-10 hierarchy codes were concordant. Cross-validation with the biological test results allowed us to validate the ICD phenotypes. Iron-deficiency anemia and diabetes mellitus were associated with a very high TPMT activity (p = 0.0004 and p = 0.0015, respectively). We describe here an original method to perform PheWAS on a quantitative trait using both ICD-10 diagnosis codes and biological test results to identify associated phenotypes. In the field of pharmacogenomics, PheWAS allow for the identification of new subgroups of patients who require personalized clinical and therapeutic management.
[Show abstract][Hide abstract] ABSTRACT: Pathologic features of Parkinson's disease (PD) include death of dopaminergic neurons in the substantia nigra, presence of α-synuclein containing Lewy bodies, and iron accumulation in PD-related brain regions. The observed iron accumulation may be contributing to PD etiology but it also may be a byproduct of cell death or cellular dysfunction. To elucidate the possible role of iron accumulation in PD, we investigated genetic variation in 16 genes related to iron homeostasis in three case-control studies from the United States, Australia, and France. After screening 90 haplotype tagging single nucleotide polymorphisms (SNPs) within the genes of interest in the US study population, we investigated the five most promising gene regions in two additional independent case-control studies. For the pooled data set (1289 cases, 1391 controls) we observed a protective association (OR=0.83, 95% CI: 0.71-0.96) between PD and a haplotype composed of the A allele at rs1880669 and the T allele at rs1049296 in transferrin (TF; GeneID: 7018). Additionally, we observed a suggestive protective association (OR=0.87, 95% CI: 0.74-1.02) between PD and a haplotype composed of the G allele at rs10247962 and the A allele at rs4434553 in transferrin receptor 2 (TFR2; GeneID: 7036). We observed no associations in our pooled sample for haplotypes in SLC40A1, CYB561, or HFE. Taken together with previous findings in model systems, our results suggest that TF or a TF-TFR2 complex may have a role in the etiology of PD, possibly through iron misregulation or mitochondrial dysfunction within dopaminergic neurons.
Neurobiology of Disease 10/2013; · 5.62 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To determine the influence of genetic polymorphisms on warfarin maintenance dose and to explicate an algorithm using the pharmacogenetic and clinical factors to determine the maintenance and/or starting dose of warfarin in South Indian patients receiving warfarin therapy.
Patients receiving stabilized warfarin therapy (n = 257) were included in the study. Single nucleotide polymorphisms (SNPs) of CYP2C9 (rs1799853 and rs1057910), VKORC1 (rs9923231, rs7196161, rs2884737, rs9934438, rs8050894, rs2359612 and rs7294), CYP4F2 (rs2108622) and GGCX (rs11676382) were genotyped by the quantitative real time-PCR method.
The mean daily maintenance dose of warfarin was found to be 4.7 ± 2.1 mg/day. Patients with the CYP2C9*1/*2, *1/*3 and *2/*3 variant genotypes required a 51.0 (2.8 mg), 60.9 (2.3 mg) and 62.2 % (2.2 mg) lower daily maintenance dose of warfarin, respectively, than those patients with the CYP2C9*1/*1 wild-type genotype (5.2 mg) (p < 0.0001). The genetic variants of CYP2C9, VKORC1 and GGCX were associated with decreased warfarin dose, except for rs7196161, rs7294 and rs2108622 which were associated with an increased warfarin dose. Genetic variations of CYP2C9 (*2 and *3), VKORC1 (rs9923231, rs7294, rs9934438 and rs2359612), CYP4F2, GGCX and non-genetic factors such as age, body weight, clinical status (post mechanical valve replacement) could explain up to 62.1 % of the overall variation (adjusted r (2) 60.2 %, p < 0.0001) in warfarin maintenance dose.
Genetic polymorphisms of CYP2C9, VKORC1, CYP4F2 and GGCX are important predictive factors of warfarin maintenance dose, and the developed algorithm will be useful to predict the required maintenance and/or starting warfarin dose in South Indian populations.
European Journal of Clinical Pharmacology 09/2013; · 2.74 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The best validated susceptibility variants for Parkinson's disease are located in the α-synuclein (SNCA) and microtubule-associated protein tau (MAPT) genes. Recently, a protective p.N551K-R1398H-K1423K haplotype in the leucine-rich repeat kinase 2 (LRRK2) gene was identified, with p.R1398H appearing to be the most likely functional variant. To date, the consistency of the protective effect of LRRK2 p.R1398H across MAPT and SNCA variant genotypes has not been assessed. To address this, we examined 4 SNCA variants (rs181489, rs356219, rs11931074, and rs2583988), the MAPT H1-haplotype-defining variant rs1052553, and LRRK2 p.R1398H (rs7133914) in Caucasian (n = 10,322) and Asian (n = 2289) series. There was no evidence of an interaction of LRRK2 p.R1398H with MAPT or SNCA variants (all p ≥ 0.10); the protective effect of p.R1398H was observed at similar magnitude across MAPT and SNCA genotypes, and the risk effects of MAPT and SNCA variants were observed consistently for LRRK2 p.R1398H genotypes. Our results indicate that the association of LRRK2 p.R1398H with Parkinson's disease is independent of SNCA and MAPT variants, and vice versa, in Caucasian and Asian populations.
Neurobiology of aging 08/2013; · 5.94 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Vitamin K antagonists (VKA) are used for 60 years in the treatment and prevention of thromboembolic disease. VKA were first used as rodenticides. There was a growing use of VKA in humans after President Eisenhower received them after a heart attack in 1955. However, the use of VKA is still challenging because they are characterized by a narrow therapeutic index and a great inter-individual variability in the dose response to the drug. This variability can partly be explained by demographic, clinical and therapeutic factors, but also by genetic variations. The main enzyme responsible for VKA metabolism is the hepatic cytochrome P450 2C9 (CYP2C9). Vitamin K epoxide reductase complex subunit I (VKORC1) is a key enzyme in the vitamin K cycle and was identified as the pharmacological target of VKA. Genetic variations affecting both CYP2C9 and VKORC1 are associated with a significant decrease in the VKA dose requirements and an increased risk of bleeding. Genotyping both CYP2C9 and VKORC1 before the initiation of VKA allows to identify a subgroup of patients with an early response to VKA therapy, that expose them to overdosage and a higher bleeding risk. More recently, a polymorphism in the gene encoding CYP4F2 has been identified and may partly explain the variability in warfarin maintenance dose by altering the metabolism of vitamin K. In addition, rare mutations have been found in VKORC1 that could explain very high VKA dose requirements and pharmacodynamic resistance.
Annales de biologie clinique. 10/2012; 70(5):539-551.
[Show abstract][Hide abstract] ABSTRACT: Two genome-wide association studies (GWASs) recently highlighted the HLA-DRA and HLA-DRB5 genes as associated with Parkinson disease (PD). However, because HLA-DRA displays a low level of polymorphisms and HLA-DRB5 is only present in approximately 20% of the population, these findings are difficult to interpret. Our aims were: (1) to replicate and investigate in greater detail the association between PD and the HLA-DR region; (2) to identify PD-associated HLA alleles; and (3) to perform a meta-analysis of our top finding. As part of 2 French population-based case-control studies of PD including highly ethnically homogeneous participants, we investigated the association between PD and 51 Single-nucleotide polymorphisms (SNPs) in the HLA-DR region. HLA-DRB1 alleles were imputed using the HLA(*) IMP software. HLA typing was performed in a subsample of the participants. We performed a meta-analysis of our top finding based on 4 GWAS data sets. Among 499 cases and 1123 controls, after correction for multiple testing, we found an association with rs660895 (OR/minor allele, 0.70; 95% CI, 0.57-0.87) within the HLA-DRB1 gene, which encodes the most polymorphic HLA-DR chain (DRβ). A meta-analysis (7996 cases, 36455 controls) confirmed this association (OR, 0.86; 95% CI, 0.82-0.91; P < .0001). SNP-based imputation of HLA alleles showed an inverse association between PD and the HLA-DRB1(*) 04 allele. We replicated an association between PD and the HLA-DR region and provided further insight into the loci and alleles involved. The highly polymorphic HLA-DRB1 locus contains rs660895, which represents a more legitimate candidate than previous ones. Our finding is in agreement with the hypothesis of an immune component in PD pathophysiology.
Movement Disorders 07/2012; 27(9):1104-10. · 5.63 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A simple, rapid, sensitive and specific ultra-high-performance liquid chromatography-tandem mass spectrometry method (Waters UPLC-MS-MS) is developed and validated for the quantification of uracil (U) and 5,6-dihydrouracil (UH2) levels in human plasma. Analytes are extracted using ethyl acetate and isopropanol after deproteination, and separated by high-performance liquid chromatography (HPLC) (Acquity UPLC BEH C18 column) in a binary mobile phase system under gradient elution conditions at a flow rate of 0.4 mL/min. 5-Bromo-uracil (UBr) is used as the internal standard. The detection is performed on a triple-quadrupole mass spectrometer via electrospray positive ionization. Multiple reaction monitoring mode using the transitions m/z 112.82 → 70.05, m/z 114.88 → 55.04 and m/z 190.83 → 117.86 is used to quantify U, UH2 and UBr, respectively. The method is linear in the concentration range of 0.625-160.0 ng/mL. The total run time is 4.5 min per injection. Nine-point calibration curve and four-points quality controls are used. Excellent linearity and precision are observed with correlation coefficient (r(2)) > 0.9999. The intra-batch and inter-batch precisions are ≤ 7.3% and ≤ 8.6%, and accuracy is ≤ 17%. The developed method is shown to be suitable for routine quantitative determination of U, UH2 and 5,6-dihydrouracil-to-uracil ratio in clinical practice.
Journal of chromatographic science 06/2012; · 0.79 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Identifying predictive biomarkers of drug response is of key importance to improve therapy management and drug selection in cancer therapy. To date, the influence of drug exposure and pharmacogenetic variants on sorafenib-induced toxicity remains poorly documented. The aim of this pharmacokinetic/pharmacodynamic (PK/PD) study was to investigate the relationship between early toxicity and drug exposure or pharmacogenetic variants in unselected adult outpatients treated with single-agent sorafenib for advanced solid tumors.
Toxicity was recorded in 54 patients on days 15 and 30 after treatment initiation and sorafenib exposure was assessed in 51 patients. The influence of polymorphisms in CYP3A5, UGT1A9, ABCB1 and ABCG2 was examined in relation to sorafenib exposure and toxicity. Clinical characteristics, drug exposure and pharmacogenetic variants were tested univariately for association with toxicities. Candidate variables with p<0.1 were analyzed in a multivariate analysis.
Gender was the sole parameter independently associated with sorafenib exposure (p = 0.0008). Multivariate analysis showed that increased cumulated sorafenib (AUC(cum)) was independently associated with any grade ≥ 3 toxicity (p = 0.037); UGT1A9 polymorphism (rs17868320) with grade ≥ 2 diarrhea (p = 0.015) and female gender with grade ≥ 2 hand-foot skin reaction (p = 0.018). Using ROC curve, the threshold AUC(cum) value of 3,161 mg/L.h was associated with the highest risk to develop any grade ≥ 3 toxicity (p = 0.018).
In this preliminary study, increased cumulated drug exposure and UGT1A9 polymorphism (rs17868320) identified patients at high risk for early sorafenib-induced severe toxicity. Further PK/PD studies on larger population are warranted to confirm these preliminary results.
PLoS ONE 01/2012; 7(8):e42875. · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Managing vitamin K antagonist (VKA) therapy is challenging in children because of a narrow therapeutic range and wide inter- and intra-individual variability in dose response. Only a few small studies have investigated the effect of nongenetic and genetic factors on the dose response to VKAs in children. In a cohort study including 118 children (median age 9 years; range, 3 months-18 years) mostly with cardiac disease, we evaluated by multivariate analysis the relative contribution of nongenetic factors and VKORC1/CYP2C9/CYP4F2 genotypes on warfarin (n = 83) or fluindione (n = 35) maintenance dose and the influence of these factors on the time spent within/above/below the range. The results showed that height, target international normalized ratio and VKORC1 and CYP2C9 genotypes were the main determinants of warfarin dose requirement, accounting for 48.1%, 4.4%, 18.2%, and 2.0% of variability, respectively, and explaining 69.7% of the variability. Our model predicted the warfarin dose within 7 mg/wk in 86.7% of patients. None of the covariates was associated with the time spent above or below the international normalized ratio range. Whether this model predicts accurately the effective maintenance dose is currently being investigated.
[Show abstract][Hide abstract] ABSTRACT: We performed a three-stage genome-wide association study (GWAS) to identify common Parkinson's disease (PD) risk variants in the European population. The initial genome-wide scan was conducted in a French sample of 1039 cases and 1984 controls, using almost 500 000 single nucleotide polymorphisms (SNPs). Two SNPs at SNCA were found to be associated with PD at the genome-wide significance level (P < 3 × 10(-8)). An additional set of promising and new association signals was identified and submitted for immediate replication in two independent case-control studies of subjects of European descent. We first carried out an in silico replication study using GWAS data from the WTCCC2 PD study sample (1705 cases, 5200 WTCCC controls). Nominally replicated SNPs were further genotyped in a third sample of 1527 cases and 1864 controls from France and Australia. We found converging evidence of association with PD on 12q24 (rs4964469, combined P = 2.4 × 10(-7)) and confirmed the association on 4p15/BST1 (rs4698412, combined P = 1.8 × 10(-6)), previously reported in Japanese data. The 12q24 locus includes RFX4, an isoform of which, named RFX4_v3, encodes brain-specific transcription factors that regulate many genes involved in brain morphogenesis and intracellular calcium homeostasis.
Human Molecular Genetics 11/2010; 20(3):615-27. · 7.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The identification of xenobiotic metabolizing enzymes (i.e., CYP) and transporters (i.e., ABC transporters) (XMET) in the human brain, including the BBB, raises the question whether these transporters and enzymes have specific functions in brain physiology, neuropharmacology and toxicology.
Relevant literature was identified using PubMed search articles published up to March 2010. Search terms included 'ABC transporters and P450 or CYP', 'drug metabolism, effect and toxicity' and 'neurodegenerative disease (Alzheimer and Parkinson diseases)' restricted to the field of 'brain or human brain'.
This review aims to provide a better understanding of XMET functions in the human brain and show their pharmacological importance for improving drug delivery and efficacy and also for managing their side effects. Finally, the impact of brain XMET activity during neurodegenerative processes is discussed, giving an opportunity to identify new markers of human brain diseases.
During the last 2 decades, much evidence concerning the specific distribution patterns of XMET, their induction by xenobiotics and endobiotics and their genetic variations have made cerebral ABC transporters and CYP enzymes key elements in the way individual patients respond to centrally acting drugs.
Expert Opinion on Drug Metabolism & Toxicology 10/2010; 6(10):1161-74. · 2.94 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Voriconazole is widely used to treat invasive aspergillosis after lung transplantation. In cystic fibrosis patients, the interindividual variability in drug disposition complicates the optimal voriconazole dosing and increases the risk of toxicity. The objective of this retrospective study was to evaluate the influence of CYP2C19 genotype on voriconazole response in lung transplant patients with cystic fibrosis.
We retrospectively studied 24 Caucasian cystic fibrosis lung transplant recipients who received voriconazole. We analyzed the influence of CYP2C19 genotype (*2 and *17 alleles) on voriconazole exposure and maintenance dose and side effects.
Heterozygous carriers of the CYP2C19*2-deficient allele required lower maintenance doses (440 ± 107 mg/day) compared with wild-type and CYP2C19*17-allele carriers (633 ± 197 mg/day and 600 ± 193 mg/day, respectively, P<0.05). The time to achieve the therapeutic range and the proportion of out-of-range concentrations were significantly higher in the CYP2C19*2 group (31.3% vs. 12.1% and 9.8% of above-range levels in the CYP2C19*1 and CYP2C19*17 groups, respectively) or CYP2C19*17 group (37.9% vs. 15.6% and 13% of below-range levels in the CYP2C19*1 and CYP2C19*2 groups, respectively) (P<0.01). No relationship was found between voriconazole toxicity and CYP2C19 status.
In this frail population, voriconazole exposure is strongly influenced by CYP2C19 genotype, and determining the genotype before voriconazole initiation may help determine the initial dosing regimen that will promptly achieve therapeutic plasma levels without producing out-of-range levels.
European Journal of Clinical Pharmacology 10/2010; 67(3):253-60. · 2.74 Impact Factor